We have recently identified a novel polypeptide that is expressed selectively by dendritic cells (DC) and that exhibits significant homology with several members of the C-type lectin family. This molecule, termed ~DC-specific C- type lectin-1" or dectin-1, facilitates physical interaction between DC and T cells during antigen presentation. With respect to the function, dectin-1: a) is expressed on the surface of DC, b) binds specifically to the surface of T cells, and c) facilitates the interaction of DC with T cells during antigen presentation. Based on the observation that dectin-1 mRNA is expressed constitutively and exclusively only by cells of DC lineage (including Langerhans cells), we have hypothesized that dectin-1 gene expression is regulated by unique, DC-specific transcriptional factors. Our specific aims are: 1) To determine whether DC-specificity of dectin-1 mRNA expression is regulated at the level of transcription (by measuring the transcriptional activity of a 3 kb promoter region of dectin-1 gene); 2) To identify the DC-specific promoter and enhancer elements in the dectin-1 gene (by constructing deletion/substitution mutants of the promoter region); 3) To determine the identity of nuclear factors that bind to promoter/enhancer elements (by gel- shift assay and foot-printing analysis); and 4) To elucidate the functional role of putative DNA binding proteins in the transcription of dectin-1 (by measuring their transactivating capacity). Not only will the proposed experiments provide a molecular basis for the development of the DC network in skin, they may also lead to the discovery of DC-specific transcriptional factors. We also believe that the knowledge derived will form both conceptual and technical bases for experiments to target gene expression within DC, a technique that may be useful in constructing transgenic animals as well as devising gene therapies that restrict the expression of exogenous genes to DC throughout the body (including epidermal Langerhans cells in skin).